title: Identification of transmembrane domain 3, 4 & 5 residues that contribute to the formation of the ligand-binding pocket of the urotensin-II receptor.
abstract: Urotensin-II (UII), a cyclic undecapeptide, selectively binds the urotensin-II receptor (UT receptor), a G protein-coupled receptor (GPCR) involved in cardiovascular effects and associated with numerous pathophysiological conditions including hypertension, atherosclerosis, heart failure, pulmonary hypertension and others. In order to identify specific residues in transmembrane domains (TM) three (TM3), four (TM4) and five (TM5) that are involved in the formation of the UT receptor binding pocket, we used the substituted-cysteine accessibility method (SCAM). Each residue in the F118((3.20)) to S146((3.48)) fragment of TM3, the L168((4.44)) to G194((4.70)) fragment of TM4 and the W203((5.30)) to V232((5.59)) fragment of TM5, was mutated, individually, to a cysteine. The resulting mutants were then expressed in COS-7 cells and subsequently treated with the positively charged sulfhydryl-specific alkylating agent methanethiosulfonate-ethylammonium (MTSEA). MTSEA treatment resulted in a significant reduction in the binding of (125)I-UII to TM3 mutants L126C((3.28)), F127C((3.29)), F131C((3.33)) and M134C((3.36)) and TM4 mutants M184C((4.60)) and I188C((4.64)). No loss of binding was detected following treatment by MTSEA for all TM5 mutants tested. In absence of a crystal structure of UT receptor, these results identify key determinants in TM3, TM4 and TM5 that participate in the formation of the UT receptor binding pocket and has led us to propose a homology model of the UT receptor.
authors.affiliation: Department of Pharmacology, Institut de Pharmacologie de Sherbrooke, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4.
authors.forename: Xavier
authors.initials: X
authors.lastname: Sainsily
authors.forename: Jérôme
authors.initials: J
authors.lastname: Cabana
authors.forename: Philip E
authors.initials: PE
authors.lastname: Boulais
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Holleran
authors.forename: Emanuel
authors.initials: E
authors.lastname: Escher
authors.forename: Pierre
authors.initials: P
authors.lastname: Lavigne
authors.forename: Richard
authors.initials: R
authors.lastname: Leduc
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D018929:Cell Culture Techniques; D002522:Chlorocebus aethiops; D003545:Cysteine / Q000235:genetics; D005020:Ethyl Methanesulfonate / Q000031:analogs & derivatives / Q000494:pharmacology; D008024:Ligands; D008958:Models, Molecular; D009154:Mutation; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014579:Urotensins / Q000378:metabolism*
chemical_list: D008024:Ligands; D043562:Receptors, G-Protein-Coupled; D014579:Urotensins; C473142:Uts2r protein, rat; C093171:methanethiosulfonate ethylammonium; C029677:urotensin II; D005020:Ethyl Methanesulfonate; D003545:Cysteine
keywords: G protein-coupled receptor; Molecular model; Substituted-cysteine accessibility method; UT receptor; Urotensin-II